C#/C++ on iOS

I'm not sure I'd really see it as a great development environment but it might be convenient if you want to try things out, and now you can get C# (Mono) on your iPhone/iPad from the App Store from developer Yauheni Shauchenka.

There's also C++ and some other languages available as well. I'm guessing that though you can compile, edit and run these on the iPhone etc, that's all you can do. There's probably no native interaction so you can't use these to write software for the iPhone.